let key = 10;
let ans = "{";
for (let i = 0; i < key; i++) {
    let index = "";
    for (let j = 0; j < 10; j++) {
        index += Math.round(Math.random());
    }
    i === key - 1 ? ans += '"' + index + '"' : ans += '"' + index + '"' + ',';
}
ans += "}";
console.log(ans);